I need to test the feed to a Brushless DC servo motor from its amplifier. I have heard the DC voltage approximates an AC sine wave by supplying a full positive full negative voltage. Does this mean to get an accurate voltage reading i need my multimeter set to AC and not DC volts.

 

That ac sinewave is due to the emf fed back by the motor. I'm not sure, but maybe connecting a diode between the motor and controller and checking with a multimeter before the diode with it set to dc will show the correct reading.